This invention is in the field of implantable medical devices that are used to inject medication into the vascular system of a human subject.
There are many catheters that are used to deliver drugs into the vascular system of human subjects. Most of these catheters are open-ended which allows blood to flow into the catheter when no drug is being delivered. Although this is quite acceptable for short-term use, for catheters that remain implanted in a human subject for a time period between weeks and years, any open-ended catheter requires frequent flushing with saline solution or heparin to retain catheter patency. Although some catheters having a slit valve at their distal end to reduce this problem, there is still some opening possible between the sides of the slit where some blood can enter the catheter over long periods of time which can result in catheter blockage.
In U.S. Pat. No. 4,657,536, F. D. Dorman describes a check valve that can be used at the end of an indwelling catheter. However, Dorman""s check valve does not have a flexible tip to minimize damage to the arterial wall during placement and for preventing damage to the wall of a blood vessel if the catheter remains implanted for several years. Furthermore, the Dorman check valve does not have a continuously smooth outer surface which lack of smoothness can cause some accumulation of blood clots that could interfere with the operation of the valve. Still further, Dorman does not teach the use of a catheter check valve in conjunction with an implantable drug port where the use of an improved, long-lived check valve would be particularly valuable.
The present invention is a check valve for placement near the distal end of a catheter. This check valve has an extraordinarily simple design so that it would operate in a highly reliable manner. The check valve design allows for a continuously smooth outer surface for the catheter with check valve system so that there is no propensity for a blood clot to form in cracks on the system""s outer surface. The check valve is also designed specifically to disallow any part of the valve from separating from the catheter. This attribute prevents the creation of a foreign body that could pass downstream and cause blood flow to be stopped at some part of the vascular system.
The check valve is a formed from a low durometer, highly elastic, elastomer cylindrical tube that is shrunk into a cylindrical groove that would typically be located near the catheter""s distal end. When pressurized fluid is injected through the catheter, the cylinder that is placed over one or more holes in the cylindrical groove in the catheter is forced to expand radially outward which allows the fluid to be injected into the blood vessel. When the pressure is removed, the elastomer tube retracts to its normal position which position tightly covers the holes thereby preventing any blood from entering the catheter.
The catheter can be designed to have a flexible tip and a generally hemispherical shape at its distal end so as to decrease the chance of any damage to a vessel wall during insertion or long term use of the catheter. Furthermore, the catheter with distal check valve system is ideally suited to be used with an implanted drug port for the long-term administration of drugs. Such drug administration may take place over a period of years. To retain patency for such a long-term indwelling catheter, present practice is to use a slit-valve at the end of the catheter and/or to frequently flush an open-ended catheter with heparin or at least with a saline solution. An important advantage of the present invention is that a catheter with such a check valve could retain its patency within the vascular system of a human subject for many years without ever requiring flushing of any sort and without even having a crack in the catheter""s wall. Not requiring frequent flushing would save on the time and expense of medical personnel and would be less painful for the patients. The present invention, when in the form of a pass-through drug port, is ideally suited to be used in conjunction with an implanted cardiosaver system as described in U.S. patent application Ser. No. 10/051,743 by R. E. Fischell, et al.
Thus an object of this invention is to have a catheter that is placed for weeks to years within a blood vessel of a human subject, which catheter has a check valve with a continuously smooth outer surface to preclude any blood clot from forming on that outer surface.
Another object of the invention is to have a generally hemispherical distal end of the catheter that is also of a soft plastic so as to reduce the possibility of damage to the vessel wall during insertion and long-term usage.
Still another object of this invention is to form the check valve from a single cylindrical tube of a low durometer, highly elastic elastomer that is fixedly attached within a cylindrical groove near the catheter""s distal end, which groove provides further assurance that the cylindrical tube will not inadvertently become separated from the catheter.
Still another object of this invention is to shape the distal and proximal ends of the cylindrical tube check valve to be angled with respect to the longitudinal axis of the catheter to create a connection between the cylindrical tube and the catheter that provides for a continuously smooth outer surface where the cylindrical tube joins the catheter.
Still another object of this invention is to have the catheter filled with a solution after completion of a drug injection, which solution has essentially the same osmolality as blood so as to prevent any salts or liquid within the blood from passing by osmosis through the wall of the catheter into the catheter""s lumen.
Still another object of this invention is to have the catheter filled with a solution after completion of a drug injection, which solution includes an anti-bacterial agent to prevent bacteria from growing within the catheter.
Still another object of this invention is to use the check-valved catheter system with an implanted drug port for the long-term administration of fluids into a human subject.
These and other objects and advantages of this invention will become obvious to a person of ordinary skill in this art upon reading the detailed description of this invention including the associated drawings as presented herein.